Drill stem for flush joint drilling apparatus



July 25, 1933. R. w. CRAIG DRILL STEM FOR FLUSH JOINT DRILLING APPARATUS Filed Oct. 8, 1929 INVENTOR Patented July 25,1933

PATEIQToF F C 30 m. mm, ommmm, onriromvm, Assrzuoit TO THE ivl r oimnsurrry coMrruvY,onvrornnqpm nconronArroivoromo nmrin s'riim roia FLUSHFQIYN'JZ pnrrrnve-Arrnnniios 7 I m lication fired October a, leeafsejriai no. 395,176.

7 My invention relatesto well drillin'g 'ap--- paratus and more particularly to a novel drill stein for use in connectionjwith a 'rotary drilling apparatus having a stufiing box A in the top of a casing head,*in which stuf fing box a flush-joint drill pipe-andstem is run.

'- In --drilling oil wells u'nder j conditions Where the rock pressures encountered must be, held; in checkYorundercontrolin orderto prevent the gas from flowing around the drill stem 'at'the'top of thewell, drill pipes having joints flush with'theiouter surfaces of the drill "pipe sections have been proposed, the drill pipe jbeingfr'eciprocable 'andjrotat- -able, with a fluid-tight fit' in the stuffing boxes on the upper ends of the casing-heads in which the drill pipesiwork. For drilling' wells under theconditions specified I have designed a novel drill stem having its upper portion non-circular, preferably rectangu lar, to fit a correspondingly-shaped open' ing in the drivevbushingin a 'rotarydrilling machine and having its lower portion cir cular injcross-section and] fitting in the stulf-v ing box on ,the'itopkofithe casing head, the

diameter of the lower portionbeing'the same as that ofthe'fdrill pipe fand the joint members which connect the sections of the drill Y to provide for thecontrol of the rock pres:

. pipe'in series.-

7 shown insection. Fig, 1 shows'a drill stem provided with thefirst short orpony joint Referring to the: accoinpanyingdrawing, I Fig. 1 shows asidef'elevation of ,myflnovel' drilling stem-inconnection with a rotary ,tableand'a casing head ands drill pipe carried by the drurstem, some-parts being omitted and'other parts beingbroken off or section? Fig.) 2 is {an elevation of the'drill drill pipe section substitutedfor'the three ponyjoints'shownin Fig.3. f; I

On the 'drawing il designatesfa rotary table driven by anvsuitable means, not shown.

The table hasi the drive bushing. 2'containing the slips 8 in which the rectangular upper section 4 of'the drillstern;5 slidingly fits,

the lower section 6' of;the drillstem' being circular 'in crosssection and rotatable. and reciprocable in the stuffing box'7 on the upper end of the casing head-8 on the upper end .ofthe well: casing, not shown. The lower end of the drill stem-section 6 is se curedby the pipe joint me1nbersx9 to ;.the-

upper: end ofthe drill pipe sectionlor pony oint 10 whose lower end is secured by pipe joint membersll-ito tliefupper end of a full length drill pipe section 12. v The latter is se-' cured by the :pipe joint members 113 to the upperf end of asecond' full-lengthdrill pipe section} 14:, "to :which other drill pipe sections, not shown, are connected; in a manner =well known, The sections 12Jand 14 are each as sumed. to be about three times the length of the pony joint or the drill stem section 63.

I prefer to make my drill stemlaboutlti feet inflen'gth and'to have each ofthe sections .4 and 6 about 8-feet long. Accordingly,cduring drilling operations the travel ofthe drill stem 5 is limited to; the distance between: the table ,1 and the stuffing box 7 which distance is about equalto thel'ength of the section 6 of-thevdrill stem.

until the drilling of the well has proceededto I i is It is not necessary to us the drill.'stem, ;5-

such-a depththat it is necessary or-advisable box 7 is-not 'usfledanditheQdrilling proceeds in' the usual manner wherein a standard drill stem about 32- feet long, for example, is, employed, it being rectangular in cross-section froniend to end... With a. full length section of drill pipe connected belowyto the :drill sure. 'Untilthis depth isreachedthe stuifing.

string and. above to the lower. end .ot the, drill stem which-isslidingly fitted in the table, the latter is;rotated,1the drill string being glowered as the drilling proceeds until the top. of the drill stem reaches the table.

The drill stringis then raised 'untilthe; top

of the upper section of the drill string is above the table whereupon) the drill" string, is ens-j I pended and the drill stem'detached frointhe string and-"another section of drill pipe is attached thereto. The, string is lowered with the drill stern attached tothe top 'thereot. I The v tablel isfagai'n rotated until thetop' of the drill' 'stein' reaches the 1 table whereupon Tthei deemed advisable to attach the stuffing boX 7.

v to the casing head 8 and to substitute the drill stem for the standard allrectangular stem.

Assuming that the drillpipe section 12 was the last sectionadded-when drilling with the said standard 'drill stem and that the drilling stopped when the upper end of the section 12 was about 12 feet or twice the length of the drill steinsection 6 belowthe table 1, the drill string is raised as bring the upper end of the section 12 above theltableu The drill string is there suspended, the standard drill stem'is removed, the pony joint is connectedto the upper end of the section 12, and my drill stem 5 is Connected to the upper end of the pony joint .10. The drill string is then lowered until it rests on the bottom of the wel'lhole when: the parts'will be as in Fig. 1, whereupon the lower end of the rectangular drillstem section 4 is in the table 1, as'shown in Fig; 1. The table is rotated caus ing the drill string. to be rotated, the latter being lowered as the drilling: proceeds.

' WVhen the upper end-of the stem: section 4- enters the table the table is stopped and the drill string is raised and another section or ponyjoint', as 15, is inserted between the stem 5* andthe pony joint 10; The string is again lowered and the'dri'lling again proceeds, with the parts as in Fig. 2, until the upper end of the stem section la'gain enters the table whereupon'the string is raised and another p'ony joint, as 16, is inserted between thesteni 1 section 4 and the ponyjoint 15. 'Thestring is again lowered and the'drilling againproceeds,- with the parts as in Fig. 3 until the upper end of the stem section 4" again enters the table whereupon the string is raised m til the section12 is above the table. The string is there suspended and the three pony joints, 10, 15- and 16 are removed'and full length drill pipe section 17 whose length is" about equalto the combined lengths of the said three pony j oints,is attached to the section 12. Then the drilling proceeds 'asbew fare, th'e'pony joints 10, 15 and 16 being" again insertedin the drill string as 'before'de scribed The cycle'of attachingthepony joints serially, then removing them and then attaching a full length joint or drillpipe sectionto the string is repeated as many times asmay be required or desired.

.Ido not restrict my invention to theuse of drill stems or the sections 4: and 6 thereof to any definite lengths nor to the number of pony joints to be used serially before substituting a regular full length stem therefor.

' short 0 Ponyjoint would require'the drill stem to be about 64 feet long in order to drill of the sections will lose driving connection 'with the rotary table. The maximum distance drilled at one operation is equal to the distance the lower end of the section 4 travels from 'itshighest" driving connection withthe table to the top of the stufling box.

The length ofthe longest pony joint to be inserted and used in the string equals the depth drilled at the last drilling operation.

If the pony joint is longer than that depth the section 4' will lose driving connection with the rotary tablewhen the string is low ered so-that itstands on the bottom of the well hole. The pony joint should not exceed in length the depth ofthe lastdrilling op .eration whether-or notthe lower end of the section 4 descended during the operation the 4*":

entire way to the stuffing box, 1 7 It is1to' be understood that the drill stem 5 and-the pony joints need not be used in .ordinary drilling operations when there are no indications that-'high'pre'ssure is to be encountered in the well, to such indica-' tions adrill stcm 0ncircular in cross-section from end to end would be used with which there fwould be nowcirc ular portion working in a stuffing box on the top ofth'e casing head. In such cases no stuifing box would be used. But when gas pressure in the well-is anticipated thenthe stulling box mustbe used and around drill stemsection is necessary. If a flushjoint drill pipe is to be used with. that drill stem, itwould, be necessary to use pony joints, the length of each not being greater than the [depth the hole was drilled at the last drilling opera- It is advisable to'make the stem 5 of a sin gle jointless piece. Due to rather crude field conditions it is generally impossible to provide and'maintain an exactalinement ofthe center linesof the stufling box and the rotary i.

its

table with the resultthat the portion ofthe drill pipe or stem between the table and stuffing, box is subject to fatigue stresses that eventually produce failures where the drill stem is made of twosections screwed together,.for example, at the junction of the sections at and 6. i I Y -,I.claim:, v W 'In a rotary well drilling apparatus, a

:01; tbl th: t' To use full length jolnts in place of the, 1 My a 6 W1 a Yer lcal non clrculal opening, acasing headbelowthe rotary ta ble, a stuffing honor) the casing head spaced I r V j below; the table, flush-joint circular drill the usual 32 feet at each operatlon ofthc' pipe comprising a tandem series of relative- 1y long lengthsand embraced thelstufling,

drill stem having an upper portion with a cross-section corresponding to that of the said opening and having also a lower circular portion rigid therewith and having the same diameter as the drill pipe lengths, the lengths of the two sections of the drill stem being substantially the same.

ROBERT W. CRAIG. 

